Canker is a proliferative growth of the frog of the hoof that can extend into neighboring tissues of bar and sole. Canker appears as a red, white or gray lumpy or spongy mass that grows in thick ridges, often with a cheesy, flaky, or weepy surface. It usually is accompanied by a bad odor.

The cause of canker is not entirely known, but is likely caused or perpetuated by bacteria that proliferate in wet, contaminated footing. Canker does occur more often in horses that are stalled in consistently moist or dirty conditions, and it is worsened by long-term hoof neglect. Interestingly, though, it can occur in horses receiving excellent hoof care and management. Canker may have an auto-immune component (the body fighting against it's own tissues). Bovine Papilloma Virus, thought to be a cause of equine sarcoids, may be related to the development of canker.

DIAGNOSIS is usually pretty obvious through examination, but it can be confused with wounds to the sole, and thrush. The resulting mass of tissue in canker is usually painful when pressure is applied, and when allowed to become severe, can cause lameness. One obvious identifying feature of canker is that it bleeds easily when scraped. Biopsy confirms the diagnosis, but is not often needed unless treatment is unsuccessful.

In its early stages, canker can be misdiagnosed as thrush, which is a completely different and much less less severe condition that is treated differently. Canker is excessive tissue growth. Thrush is a destructive process in which the external tissues deteriorate and die.

TREATMENT: The principle treatment begins with careful trimming of the hoof, followed by surgical debridement of the abnormal tissue. This should be done without disruption of the normal regenerative dermal layer underneath, so it is not a matter of simply hacking off the tissue. Freezing of the remaining layer with liquid nitrogen may also be helpful.
Treatment only works if the hoof is treated aggressively after surgery, maintaining the sole clean and dry, and application of a variety of antibacterial and drying preparations. It can take weeks and repeated surgery and other treatments to resolve this stubborn problem. Oral steroids may have a place in treatment, reducing the immune component of the disease.